Enhanced Geothermal Systems

Geothermal Technologies Program

Enhanced Geothermal Systems

As charged by Secretary Abraham, the Office of Energy

Efficiency and Renewable Energy provides national leadership to revolutionize energy efficiency and renewable energy technologies, to leapfrog the status quo, and to pursue dramatic environmental benefits. The Geothermal Technologies Program, a critical part of our overall effort, is making great strides toward increasing the viability and deployment of geothermal heat and power. The peer reviewed, focused R&D and supporting outreach activities conducted by this program will enable broad expansion of the use of geothermal resources throughout the western United States. Through federal leadership and partnership with states, communities, industry, and universities, we will ensure that geothermal energy is established as an economically competitive contributor to the U.S. energy supply. Our program’s success will mean a stronger economy, a cleaner environment, and a more secure energy future for our nation.

David K. Garman Assistant Secretary Energy Efficiency and Renewable Energy

Cover image PIX07667 J.L. Renner/INEEL

Enhanced Geothermal Systems How to extract more energy and power from geothermal resources

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The Navy I geothermal power plant near Coso Hot Springs, California.

he Coso geothermal project, located in California’s Coso volcanic field and about 100 miles (161 kilometers) north of Los Angeles, produces 260 megawatts of geothermal energy. Without tapping into any new geothermal resources (just by fracturing the existing reservoir), Coso will soon produce another 20 megawatts of electricity. The additional power will come from applying technology designed to improve the production of fields like Coso. Known as enhanced geothermal systems (EGS), this technology should more than double the amount of recoverable geothermal energy in the U.S., as well as extend the productive life of existing geothermal fields. EGS Benefits • Increased Productivity • Extended Lifetime • Expanded Resources • Siting Flexibility • Sizing Flexibility • Environmental Advantages With EGS, a new reservoir is targeted within a volume of rock that is hot, tectonically stressed,

PIX07667 J.L. Renner, INEEL

and fractured. However, due to secondarymineralization processes, those fractures have sealed over time, resulting in low permeability and little or no production of fluids. Through a combination of hydraulic, thermal, and chemical processes, the target EGS reservoir can be ‘stimulated,’ causing the fractures to open, extend, and interconnect. This results in the creation of a conductive fracture network and a reservoir that is indistinguishable from conventional geothermal reservoirs. EGS technology could serve to extend the margins of existing geothermal systems or create entirely new ones, wherever appropriate thermal and tectonic conditions exist. The enhanced production at Coso will come as DOE’s partners at the University of Utah’s Energy & Geoscience Institute (EGI) and Caithness Corporation pump water under high pressure into a portion of the Coso field to reopen sealed fractures in subsurface rocks. Water pumped into the ground from injection wells will then circulate through the fractured rocks, flow to the surface through existing geothermal wells, and drive steam turbines. The process, called “hydrofracturing,” is commonly used in oil and gas production. “We are attempting to tap into less 3

permeable and less productive margins of existing geothermal systems,” according to Peter E. Rose, coordinator of the Coso EGS project at EGI. For upto-date information on this project, see the Coso EGS website at: egs.egi.utah.edu/indexcoso.htm.

Pipeline for Field Distribution Provided by Unocal and Calpine

Pump Stations Electricity provided by Unocal and Calpine

Geysers Project, California The Geysers, about 120 miles (193 kilometers) north of San Francisco, is the world’s largest dry-steam geothermal steam field, reaching peak production in 1987, at that time serving 1.8 million people. Since then, the steam field has been in gradual decline as its underground water source decreases. Currently, The Geysers produce enough electricity for 1.1 million people.

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Geysers Storage Tank Provided by City

P#3 Pine Flat (uphill segment)

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EGS techniques will also increase the production and extend the life of The Geysers geothermal steam field. At The Geysers, Calpine Corporation and the Northern California Power Agency have found a way to generate more electricity without tapping additional geothermal resources. They are recharging existing reservoirs with treated wastewater from nearby communities. The companies, in partnership with the City of Santa Rosa, have built about 40 miles (64 kilometers) of pipeline to carry treated city wastewater to The Geysers.

Alexander Valley

PIX00060 Pacific Gas & Electric

Pipeline to Geysers Storage Tank Provided by City

Santa Rosa Plain

Pump Station #1 Electricity provided by City Delta Pond, Santa Rosa

The wastewater from the Santa Rosa project will be injected into underground wells at a depth of 7,000 to 10,000 feet (2,134 to 3,048 meters), and at a rate of 11 million gallons (50 million liters) a day for the next 30 years. This water will be naturally heated in the geothermal reservoir, and the resulting steam will be used in nearby power plants to produce electricity. The project should increase electrical output by 85 megawatts, enough for about 85,000 homes. A view of several geothermal power plants at The Geysers, northern California (showing water-vapor emissions during normal cooling operation). 4

EGS seeks to tap a continuum of geothermal resources, ranging from conventional hydrothermal resources to hot dry rock. Nature has been prolific in providing large quantities of heat in the earth’s crust, but fluids and permeability are less abundant. With EGS, we hope to “engineer” new and improved reservoirs, and foster the economic production of that heat over long periods of time. Similar research and demonstration efforts are well underway in

EGS Around the West

Europe (websites at www.dhm.ch/dhm.html and www.soultz.net) and Australia (website at: hotrock.anu.edu.au), and show the promise of EGS technology worldwide. EGS technology will initially enable greater efficiency and sustainability in the extraction of heat energy from producing hydrothermal fields. The technology developed will also set the stage for eventually recovering the abundant heat contained in areas not associated with commercial hydrothermal fields, but with huge resource potential. This broadening use of geothermal resources will strengthen security and develop needed, clean, domestic energy resources. ■

DOE Program Goal – Enhanced geothermal systems should increase geothermal production to 20,000 MW by 2020.

PIX 07655 Joel Renner, INEEL

A similar project with the Lake County Sanitation District called the Southeast Geysers Wastewater Recycling System has been operating successfully since 1997. This system delivers about 2.8 billion gallons (10.6 billion liters) of effluent annually, and has delivered more than 16 billion gallons (60.5 billion liters) of fluid to The Geysers since operations began. This project was described in the 1999 Geothermal Today in an article titled Turning Wastewater into Clean Energy.

Located in Siskiyou County, California, about 30 miles (48 kilometers) south of the Oregon border, Calpine Siskiyou Geothermal Partners is developing and demonstrating new EGS techniques. Specifically, they are developing stimulation technology to extract energy from reduced permeability zones around geothermal wells. This EGS project is part of a larger development that could result in two geothermal power plants that each produces 50 The Steamboat geothermal power plant, originally built and now megawatts of electricity. The plant goes online in owned by ORMAT, in Steamboat Springs, Nevada. 2004, and Calpine already has a power purchase agreement with Bonneville Power Administration. of this project will be the drilling, logging, hydraulic fracturing, ORMAT Nevada, Inc., a major geothermal operator, plans to and testing of the reservoir, followed by the construction apply EGS techniques at a prospective geothermal site east and operation of a facility employing EGS technology for of the operating Desert Peak geothermal field in Churchill commercial power generation. County, Nevada. They will fracture a low permeability zone under the ground to enable production of an estimated 2 to 5 The project seeks to demonstrate that: 1) hydraulic fracturing megawatts of electricity. If successful, this project could have technology can be applied commercially to geothermal wide application to other geothermal sites in the Great Basin, systems; 2) adequate analytical techniques (such as subsurface due to the many similarities of subsurface features throughout stress analysis, fracture definition through seismic monitoring, this geologic province. numerical simulation of fluid flow and heat transfer in fractured media, etc.) required for an EGS project are already available; The DOE will share the cost of the Phase I feasibility study of a 3) neither water loss nor cooling of the produced fluid is a three phase, five-year program to develop a commercial EGS prohibitive barrier to a well-designed EGS project; and 4) power plant project. ORMAT’s objective will be to develop commercial power can be generated reliably from an EGS and demonstrate EGS techniques at its geothermal leasehold project. The project relies upon proven technology for reservoir area, east of the existing Desert Peak Geothermal Facility in characterization and routine wellfield/power plant operation, Churchill County, Nevada. The objectives of subsequent phases and the application of existing fracturing technology to EGS.

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Energy efficiency and clean, renewable energy will mean a stronger economy, a cleaner environment, and greater energy independence for America. By investing in technology breakthroughs today, our nation can look forward to a more resilient economy and secure future. Far-reaching technology changes will be essential to America’s energy future. Working with a wide array of state, community, industry, and university partners, the U.S. Department of Energy’s Office of Energy Efficiency and Renewable Energy invests in a portfolio of energy technologies that will: * Conserve energy in the residential, commercial, industrial, government, and transportation sectors * Increase and diversify energy supply, with a focus on renewable domestic sources * Upgrade our national energy infrastructure * Facilitate the emergence of hydrogen technologies as vital new “energy carriers.”

Biomass Program Using domestic, plant-derived resources to meet our fuel, power, and chemical needs Building Technologies Program Homes, schools, and businesses that use less energy, cost less to operate, and ultimately, generate as much power as they use Distributed Energy & Electric Reliability Program A more reliable energy infrastructure and reduced need for new power plants Federal Energy Management Program Leading by example, saving energy and taxpayer dollars in federal facilities FreedomCAR & Vehicle Technologies Program Less dependence on foreign oil, and eventual transition to an emissions-free, petroleum-free vehicle Geothermal Technologies Program Tapping the Earth’s energy to meet our heat and power needs Hydrogen, Fuel Cells & Infrastructure Technologies Program Paving the way toward a hydrogen economy and net-zero carbon energy future Industrial Technologies Program Boosting the productivity and competitiveness of U.S. industry through improvements in energy and environmental performance Solar Energy Technology Program Utilizing the sun’s natural energy to generate electricity and provide water and space heating Weatherization & Intergovernmental Program Accelerating the use of today’s best energy-efficient and renewable technologies in homes, communities, and businesses Wind & Hydropower Technologies Program Harnessing America’s abundant natural resources for clean power generation To learn more, visit www.eere.energy.gov

Produced for the

1000 Independence Avenue, SW, Washington, DC 20585 By the National Renewable Energy Laboratory, a DOE National laboratory DOE/GO-102004-1958 August 2004 Printed with renewable-source ink on paper containing at least 50% wastepaper, including 20% postconsumer waste